Control system for a motor vehicle automatic gearbox and method for operating said control system

ABSTRACT

In a control system ( 20 ) for an automatic motor vehicle transmission ( 10 ), with a number of gear selection modules ( 38, 40, 42 ), each of which is respectively designed to preset a target gear (zg) for a gear change depending on a number of operating parameters, through a suitable use of gear change prevention means, a particularly simple and transparent adaptation of the vehicle behavior to different driver requests should also be possible. To that end, the invention provides a number of analysis modules ( 46, 48, 50 ), each of which, in a respectively predeterminable operating situation, generates a suppression signal (u) for preventing a gear change, where each analysis module ( 46, 48, 50 ) is associated with a respective filter element ( 52, 54, 56 ), which enables the transmission of the respective suppression signal (u), depending on which gear selection module ( 38, 40, 42 ) has preset the target gear (zg). Preferably, a central control module ( 60 ) contains information, in the form of an applicable matrix for each analysis module ( 46, 48, 50 ), which indicates the target gear (zg)-presetting gear selection module ( 38, 40, 42 ) for which the suppression signal (u) is to be transmitted.

The invention relates to a control system for an automatic motor vehicletransmission with a number of gear selection modules, each of which isdesigned for presetting a target gear for a gear change depending on anumber of operating parameters. The invention also relates to a methodfor operating a control system of this kind.

In a motor vehicle with an automatic transmission, in particular with anautomatic stepped transmission, a control system can be used in which anautomatic control unit determines a gear that is suitable for eachdriving situation. In this case, depending on operating parameterscharacteristic of the driving situation, e.g. the vehicle speed, enginespeed, and/or a lateral acceleration, the best gear for the drivingsituation determined from these parameters, is established as the targetgear. The selection of the gear suitable to be the target gear can takeplace in particular through evaluation of characteristic curvesregarding the throttle valve position and vehicle speed stored in thecontrol system or also through determination of an optimal engine speedand subsequent discretization, i.e. association with the gear whosespeed spectrum covers the optimal engine speed. If the target gear,which is determined in this manner, differs from the currently set gear,then a shift from the current gear into the target gear can be requestedand a shifting command that triggers it can be given.

Alternatively or in addition to such a presetting of the target gear,there can also be a manual presetting of a target gear, which can beactivated as desired by the driver. For example, the driver can inputthe target gear directly by means of a selector lever. A control systemfor the automatic motor vehicle transmission, which system is designedto take into account such a manual input, consequently includes a numberof gear selection modules, each of which is designed for presetting atarget gear under different boundary conditions. A first of these gearselection modules can preset the target gear after the fashion of anautomatic control by evaluating measurement values, which arecharacteristic for the driving situation, as operating parameters. Bycontrast, another gear selection module can be designed to preset thetarget gear based on operating parameters manually input by the driver.Furthermore, additional gear selection modules can be provided, whichare respectively adapted to other driving situations or operatingparameters. As soon as one of these gear selection modules, which areconnected in parallel in terms of logic, presets a target gear, then agear change into this target gear can be executed.

However, despite the fact that a target gear has just been preset by oneof the gear selection modules, in certain driving situations, it can bedesirable not to shift into this target gear immediately. For example,when cornering at a relatively high speed, it can be desirable not toshift gears in order to prevent possible instabilities while negotiatingthe curve. In another case, it can be desirable to reliably preventso-called oscillating gear changes. Oscillating gear changes can occurwhen one or more of the operating parameters, which determine gearselection, changes in a way that would produce a continuous series ofupshifts and downshifts.

For such situation-dependent shift prevention, the control system caninclude a number of analysis modules, each of which, when a respectivelypredeterminable operating situation occurs, generates a suppressionsignal to prevent a gear change. Predeterminable operating situationsthat can be taken into account include, for example, situations thatcould lead to the above-mentioned oscillating gear changes, or asituation such as “high-speed cornering”. The suppression signal can beconsulted in the control system in such a way as to ignore the shiftingcommand, which is generated as a result of the presetting of a targetgear by one of the gear selection modules, or to prevent this shiftingcommand from being executed.

DE 196 24 061 A1 has disclosed a method for controlling the gearchanging of an automatic motor vehicle transmission, which is designedto prevent oscillating gear changes. With this method, a shiftingcommand to change gears into a target gear is only executed when anumber of predeterminable criteria are fulfilled. In order to preventoscillating gear changes, there is the particular provision that as onecriterion, a parameter-dependent minimum waiting time must pass after agear change is executed before a new gear change can take place.However, on the one hand this method is only aimed at preventingoscillating gear changes and on the other hand, it does not directlyprovide an equal treatment of several gear selection modules, which areused to preset a target gear, and consequently can be used with only alimited degree of flexibility.

The object of the invention, therefore, is to disclose a control systemfor an automatic motor vehicle transmission of the type mentioned above,which through a suitable use of gear change prevention means, alsopermits a particularly simple and transparent adaptation of the vehiclebehavior to different driver requests. The object is also to disclose amethod particularly suited to operating the control system.

As regards the control system, this object is attained by providing anumber of analysis modules, each of which, when a respectivelypredeterminable operating situation occurs, generates a suppressionsignal to prevent a gear change, where each analysis module isassociated with a respective filter element, which enables therespective suppression signal to be transmitted depending on which gearselection module has preset the target gear.

The invention is based on the realization that a particularly simpleadaptation of the vehicle behavior to different requests can also beachieved by suitably combining on the one hand, a number of possiblesources for the respective parameter-dependent presetting of a targetgear and on the other hand, a number of possible modules for assuringthe prevention of gear changes in a demand-controlled fashion. In thisconnection, the integration of several gear selection modules, which isembodied in the form of a parallel processing of several sources and isdesigned to preset the target gear, permits a target gear to becorrespondingly preset in each gear selection module depending onboundary conditions specifically stored there. On the other hand, theuse of a number of analysis modules permits a specific suppression ofundesirable gear changes to be respectively implemented in each analysismodule. However, such a multi-channel system should assure that on theone hand, a positive cooperation of all of the components is maintainedand that on the other hand, mutually contradictory presets and shiftingcommands are reliably prevented. To that end, for each analysis module,a filter module is implemented, which from this standpoint, stops orpermits the transmission of the possibly generated suppression signal.In particular, there is the provision that the origin or source of thetarget gear preset is taken into account in the decision governingwhether a target gear preset for generating a shifting command is to betransmitted or be suppressed due to specific driving considerations.

The filter elements can each be integrated directly into thecorresponding analysis modules, in the form of a decentralized design.In this instance or in an alternative possible combination of filterelements to form central filter component, a central control module cansuitably control the filter elements, thus assuring a systematic andconsistent cooperation of the filter elements.

For a particularly high degree of flexibility of the control system, thecentral control module advantageously contains information, in the formof an applicable matrix for each analysis module, which indicates thetarget gear-presetting gear selection module for which a possiblygenerated suppression signal is to be transmitted. In this embodiment,the control module is embodied in the form of a criteria administrator.The form of the applicable matrix can also be used, for example, tostore information indicating that a suppression signal generated by the“oscillating gear change prevention” analysis module is to betransmitted inside the control system if the presetting of the targetgear originates from an automated control block as a gear selectionmodule, but that the suppression signal is not to be transmitted if thepresetting of the target gear originates from a selector lever as thegear selection module, which is actuated directly by the driver.Consequently, a presetting can be achieved in a particularly simplemanner, which on the one hand, should reliably prevent oscillating gearchanges in automatic gear selection, but which on the other hand, shouldimmediately respond to the driver commands in manual gear selection.

Storing the association, which indicates the presetting gear selectionmodule for which a suppression signal is to be transmitted and theanalysis module to which it belongs, in the form of an applicable matrixin the central control module also assures a particularly high degree offlexibility and in particular, an ability of the control system to beused, which is not limited to the concrete vehicle type. For example,there can be a different prioritization of individual gear selectionmodules depending on the vehicle type: in a more sport-oriented vehicletype, for example, a manual gear presetting can be given a higherpriority than an automatically generated gear presetting. In this case,when a target gear is manually preset, an oscillating gear changeprevention can be suppressed, whereas when a target gear isautomatically preset, an oscillating gear change prevention would bepermitted. By contrast, in a vehicle type oriented more toward leisurelydriving, an oscillating gear change prevention would be permitted withboth manual and automatic presetting of the target gear. The controlsystem, particularly with regard to its hardware components, can be usedequally for both of these types, where the individual adaptation to therespective vehicle type can be executed merely in the form of thecorresponding modification of the applicable matrix stored in thecontrol module and can consequently be executed at a comparatively lowcost.

In order to directly influence the suppression signals generated by theanalysis modules, the central control module is suitably connected onthe output side to each filter element associated with a respectiveanalysis module, in order to transmit an enable signal. The enablesignal can thereby “open” the filter element and consequently permit thetransmission of a possibly existing suppression signal.

The taking into consideration of the origin of the presetting of therespective target gear can be achieved in a particularly simple mannerin that, in an advantageous embodiment, each gear selection module, inchronological connection with the presetting of a target gear,respectively sends a signal, which identifies the presetting gearselection module, to the filter elements or to the central controlmodule.

As regards the method, the stated object is obtained by virtue of thefact that a suppression signal generated by an analysis module isenabled for transmission depending on which gear selection module haspreset the target gear.

The advantages achieved with the invention are comprised in particularin that by taking the origin of a preset for a target gear into accountin the decision as to whether a suppression of the gear change into thistarget gear in the form of a gear change prevention should take place,it is possible in a particularly simple manner for there to be alogically parallel processing of different gear selections and alogically parallel processing of different criteria for gear changepreventions. In addition, by storing the corresponding association inthe form of an applicable matrix in the central control module, thecontrol system can be used in a particularly varied and flexible manner,in particular, an especially simple subsequent adaptation to modifiedpresets as well as an ability to be used universally, even in differentvehicle types.

An exemplary embodiment of the invention will be explained in detail inconjunction with the drawings.

FIG. 1 schematically depicts a drivetrain of a motor vehicle with anassociated control system, and

FIG. 2 schematically depicts the control system according to FIG. 1 indetail.

Parts that are the same in both figures are provided with the samereference numerals.

The drivetrain 1 according to FIG. 1 has a vehicle motor 2, which isconnected to a clutch 6 means of an input shaft 4. On the output side,the clutch 6 is connected by means of a shaft 8 to an automatictransmission 10, which in turn is connected on the output side or on thedriven side, by means of a driveshaft 12, to a drive unit 14 of a motorvehicle, for example by means of a driving wheel set. In the exemplaryembodiment, the clutch 6 is embodied as a hydrodynamic converter;alternatively, however, a servo-actuated friction clutch can also beprovided or another clutch, which is suitable for producing a slipping,non-positive connection between the vehicle motor 2 and the drive unit14. The automatic transmission 10 is embodied as a stepped transmissionand has a number of predefined gears, each of which is associated with afixed ratio of the speed of the shaft 8 to the speed of the drive shaft12. Supplying a shifting command S to the automatic transmission cantrigger a change between the gears.

For control purposes, the automatic transmission 10 is associated with acontrol system 20. The control system 20 is designed to determine thetransmission ratio, which is desirable for the current drivingsituation, and to set it in the automatic transmission 10 bytransmitting the corresponding shifting command S. To that end, theoutput side of the control system 20 is connected to the automatictransmission 10 by means of a signal line 22. On the input side, thecontrol system 20 is connected via a signal line 24 to the automatictransmission 10, via a signal line 26 to a speed sensor 28 disposed onthe input shaft 4, via a signal line 30 to a speed sensor 32 disposed onthe driveshaft 12, and via a number of other signal lines, which areindicated by the arrow 34, to a number of other measurement valuesensors that are not shown in detail.

As a result, an actual value for the currently set gear g can besupplied to the control system 20 via the signal line 24. The signallines 26, 30 can be used to supply the control system 20 with actualvalues for the speed of the input shaft 4, the engine speed nm, or thespeed na of the driveshaft 12. An actual value for the vehicle speed cantherefore be derived from the speed na. Alternatively, the separatedetection of the speed of each individual wheel of the vehicle can beprovided, which in addition to the vehicle speed, also permits otherrelevant measurement quantities to be derived, such as slippage of adrive wheel. Furthermore, via the other signal lines indicated by thearrow 34, the control system 20 can be supplied with actual values ofother relevant measurement values or operating parameters, for exampleby acceleration sensors, a throttle valve position, or a fuel supply,but also by an input device that allows the driver to manually input adesired gear.

The internal structure of the control system 20 is schematicallydepicted in FIG. 2. The control system 20 includes a main control unit36, which is connected to the signal line 22 in order to output shiftingsignals S and is connected to the signal line 24 in order to read in theactual value of the gear g that is currently set.

On the input side, the main control unit 36 is connected to a number ofgear selection modules 38, 40, 42. Each gear selection module 38, 40, 42is respectively designed to preset a target gear zg depending on anumber of specific operating parameters. When a preset target gear zg issupplied to the main control unit 36, this main control unit checkswhether the target gear zg agrees with the current gear g of theautomatic transmission 10. If this is not the case, then subject to thelimitations that will be discussed in more detail below, the maincontrol unit 36 transmits a shifting command S to the automatictransmission 10, which triggers the execution there of a gear changeinto the target gear zg.

The first gear selection module 38 is embodied the form of aconventional automatic gear selection device and is connected on theinput side to the signal lines 26, 30, among others. Based on number ofmeasurement values that can be supplied to it as operating parameters,in particular the speed na of the driveshaft 12 and a measurement valuethat is characteristic for the throttle valve position of the vehiclemotor 2, and based on a stored engine speed nm that is particularlyfavorable for the operation of the vehicle motor, the first gearselection module 38 determines a desired speed ratio or transmissionratio of the automatic transmission 10. Based on this and through asuitable discretization and subsequent association with the speed rangesthat are associated with the individual gears, the first gear selectionmodule 38 determines a particularly suitable target gear zg, which itsends as a preset to the main control unit 36.

By contrast, the second gear selection module 40 is designed to processa desired gear as an operating parameter, which desired gear is directlyinput by the driver and can be input, for example, by means of aselector lever or tap lever. It immediately places the desired gear,which is supplied to it via an input line 44, in readiness as a targetgear zg.

The third gear selection module 42 can, like other gear selectionmodules that may also be provided, can also be designed to prepare apreset for a target gear zg on another basis. Correspondingly, the maincontrol unit 36 can always be supplied, in the form of a parallelprocessing, with one or more presets for a target gear zg.

The main control unit 36 is also connected on the input side to a numberof analysis modules 46, 48, 50. The analysis modules 46, 48, 50 aredesigned in such a way that they generate a suppression signal u for arespective, specifically predeterminable operating situation. If therespective suppression signal u is supplied to the main control unit 36,then even if the preset of the target gear zg supplied to the maincontrol unit 36 differs from the current gear g, a gear change does notoccur and the transmission of the shifting signal S to the automatictransmission 10 is suppressed.

The first analysis module 46 here is embodied in the form of anoscillating gear change prevention means and particularly in the eventof an essentially unchanged gas pedal position, should assure theprevention of a continuous series of gear changes into the next highergear and then back into the next lower gear as a result of slightlychanging external conditions. To that end, the analysis module 46 isconnected to a number of other signal lines, which are symbolized by thearrow 34, via which the analysis module 46 can in particular be suppliedwith measurement values for vehicle speed, gas pedal position, enginespeed nm, etc.

The second analysis module 48 is embodied as a gear change preventionmeans for cornering and particularly during rapid cornering, shouldprevent an excessively early gear change into the next higher gear,which could encourage a loss of traction or other temporary instabilityin performance. To the end, the second analysis module is particularlyembodied for the detection of a “high-speed cornering” operating stateand among other things, is connected on the input side to a number ofother signal lines symbolized by the arrow 34 in such a way that it canbe supplied with measurement values as operating parameters, whichrelate to the vehicle speed and lateral acceleration of the vehicle.

The third analysis module 50 can, like other analysis modules that mayalso be provided, be embodied in the form of a gear change preventionmeans for other standardizable operating situations. Correspondingly,the main control unit 36 can always be supplied, in the form of aparallel processing, with one or more suppression signals u in order toprevent a gear change.

In other words: the control system 20 is embodied in such a way that themain control unit 36 can be supplied, in the form of a parallelpreparation, with presets for a target gear zg as well as suppressionsignals u for preventing a gear change, on respectively parallelchannels. Particularly while processing suppression signals u, a linkagein the form of a logical “OR” is executed: if at least one suppressionsignal u is present in the main control unit 36, regardless of whichanalysis module 46, 48, 50 has generated it, then the transmission ofthe shifting signal S is suppressed and a gear change is consequentlyprevented.

The control system 20 is embodied in such a way that even in the eventof a relatively high degree of complexity, on the one hand,inconsistencies in the processing are prevented and on the other hand, aparticularly high degree of flexibility is possible in the adaptation tonew or additional presets. To that end, each analysis module 46, 48, 50is associated with a respective filter element 52, 54, 56. In theexemplary embodiment, each filter element 52, 54, 56 is integrated intothe corresponding analysis module 46, 48, 50; however, the filterelement can also be embodied separately from this analysis module and beconnected after it with a view to processing the respective suppressionsignal u. Each filter element 52, 54, 56 is embodied in such a way thatit enables the transmission of a suppression signal u generated by theassociated analysis module 46, 48, 50, depending on which gear selectionmodule 38, 40, 42 has preset the target gear zg.

This assures that the origin of the preset for the target gear zg istaken into account in the decision as to whether or not a certain gearchange prevention can be permitted in connection with the gear changesought by the preset of the target gear zg. For example, the filterelement 52 associated with the analysis module 46 can be designed forthe following boundary conditions: the analysis module 46 is embodied asan oscillating gear change prevention means. Now the provision can alsobe made that an oscillating gear change prevention is to be viewed aspermissible if the preset of the target gear zg was made by theautomatic transmission control and consequently by the first gearselection module 38, but that an oscillating gear change prevention isto be viewed as impermissible if the preset of the target gear zg wasmade through manual input and consequently by means of the second gearselection module 40. An arrangement of this kind could correspond, forexample, to a sport-oriented vehicle type with an active driver type, inwhich driver commands would essentially be handled with the highestpriority.

In order to convert this boundary condition, the filter element 52,which is associated with the first analysis module 46 embodied as anoscillating gear change prevention means, can be embodied in such a waythat a suppression signal u, which is generated by the first analysismodule 46 when the danger of an oscillating gear changing is detected,is transmitted to the main control unit 36 in order to prevent a gearchange if the target gear zg was preset by the first gear selectionmodule 38, but not if the target gear zg was preset by the second gearselection module 40.

For a coordinated execution of different presets, the control system 20has a central control module 60. On the output side, this centralcontrol module 60 is connected to the filter elements 52, 54, 56 in sucha way that it can control them. In particular, the central controlmodule 60 is connected on the output side to each analysis module 46,48, 50 via a respective signal line 62, 64, 66, via which an enablesignal f can be transmitted to the filter element 52, 54, 56, which isintegrated into the respective analysis module 46, 48, 50. The filterelements 52, 54, 56 are embodied in such a way that a suppression signalu generated by the associated analysis module 46, 48, 50 is onlytransmitted to the main control unit 36 if a related enable signal f ispresent in the filter element 52, 54, 56.

On the input side, the central control module 60 is connected to each ofthe gear selection modules 38, 40, 42. The provision is made here thateach gear selection module 38, 40, 42, when it gives a preset for atarget gear zg to the main control unit 36, in chronological connectionwith this presetting, sends a signal K that identifies the presettinggear selection module 38, 40, 42 to the central control module 60.Consequently, in chronological coincidence with the target gear zgpreset given to the main control unit 36, the central control module 60contains information as to which gear selection module 38, 40, 42 is theorigin of the preset. This also permits a possibly required generationand processing of a corresponding suppression signal u and its filteredtransmission to the main control unit 36 in an updating fashion so thatthe target gear zg preset and a suppression signal u, which is possiblypresent in the main control unit 36, can be processed together in thedesired fashion.

In order to take the origin of the target gear zg preset into account ina particularly suitable fashion in the decision as to whether or not arelated suppression signal u should lead to a prevention of a gearchange, the central control module 60 contains information, in the formof an applicable matrix for each analysis module 46, 48, 50, whichindicates the target gear zg-presetting gear selection module 38, 40, 42for which a corresponding suppression signal u is to be transmitted. Thestorage of this information in the form of an applicable matrix in thecentral control module 60 permits a particularly simple exchange of thisinformation and consequently permits a particularly simple adaptation ofthe characteristics of the control system 20. In particular, this alsopermits an especially high degree of flexibility of the control system20 and its ability to be used, even in different vehicle types.

What is claimed is:
 1. A control system (20) for an automatic motorvehicle transmission (10), with a number of gear selection modules (38,40, 42), each of which is respectively designed to preset a target gear(zg) for a gear change depending on a number of operating parameters,and with a number of analysis modules (46, 48, 50), each of which, in arespectively predeterminable operating situation, generates asuppression signal (u) for preventing a gear change, where each analysismodule (46, 48, 50) is associated with a respective filter element (52,54, 56), which enables the transmission of the respective suppressionsignal (u), depending on which gear selection module (38, 40, 42) haspreset the target gear (zg).
 2. The control system (20) according toclaim 1, whose filter elements (52, 54, 56) can be controlled by acentral control module (60).
 3. The control system (20) according toclaim 2, whose central control module (60) contains information, in theform of an applicable matrix for each analysis module (46, 48, 50),which indicates the target gear (zg)-presetting gear selection module(38, 40, 42) for which the suppression signal (u) is to be transmitted.4. The control system (20) according to claim 2, whose central controlmodule (60) is connected on the output side to each analysis module (46,48, 50) in order to transmit an enable signal (f).
 5. The control system(20) according to claim 1, whose gear selection modules (38, 40, 42), inchronological connection with the presetting of a target gear (zg),respectively send a signal (K), which identifies the presetting gearselection module (38, 40, 42), to the filter elements (52, 54, 56) or tothe central control module (60).
 6. A method for operating a controlsystem (20) for an automatic motor vehicle transmission (10), with anumber of gear selection modules (38, 40, 42 , each of which isrespectively designed to preset a target gear (zg) for a gear changedepending on a number of operating parameters, and with a number ofanalysis module (46, 48, 50), each of which, in a respectivelypredeterminable operating situation, generates a suppression signal (u)for preventing a gear change, where the transmission of a suppressionsignal (u) generated by an analysis module is enabled depending on whichgear selection module (38, 40, 42) has preset the target gear (zg).